simnoise.m

阵列信号处理的工具箱

function noise3D = simnoise(noiseSources, noPulses, noRangeBins, noChannels);

%SIMNOISE is the core simulating engine for simulating noise sources.
%
%Synopsis:
%  noise3D = simnoise(noiseSources, noPulses, noRangeBins, noChannels);
%
%Description:
%  Simulates radarsignals and stores the data in a 3D matrix
%  ( Number Pulses x Number Of RangeBins x Number Of Channels )
%  The simulator assumes that the noise is borne in the antenna channels,
%  in contrast to in the antenna elements or outside of the antenna. This
%  implies that the noise signals does not pass through the analog
%  beamformer modelled by the steering matrix, e.g. the steering matrix is
%  not needed in calculations.
%  The noise that is simulated is a complex gaussian noise with mean 0 and
%  variance equal to the wanted power. The power of the noise is the same
%  in all channels. Since the noise is deployed directly in the antenna
%  channels, the signal-to-noise-ratio is ambiguous and dependent of the
%  steering matrix. If the steering matrix has components whos absolute
%  values is different from "1", then the target's power will vary from
%  antenna channel to antenna channel and thus will SNR vary equally much.
%
%  This function is called upon by the function "simradarsig" and is
%  normally not used by the end user.
%
%Input:
%  noiseSources (NoiseDefT)  : Cellarray of the noise sources that will be
%                              simulated.
%  noPulses (IntScalarT)     : Number of pulses in simulation.
%  noRangeBins (IntScalarT)  : Number of rangebins in simulation.
%  noChannels (IntScalarT)   : Number of channels of the antenna.
%
%OutPut:
%  noise3D (CxMatrixT) : 3D matrix with the simulated data.
%                        pulses x rangebins x channels.
%
%--------
%Notations:
%  Data type names are shown in parentheses and they start with a capital
%  letter and end with a capital T. Data type definitions can be found in
%  [1] or by "help dbtdata".
%
%Examples:
%
%Software Quality:
%
%Known Bugs:
%
%References:
%  [1]: Bj鰎klund S., Rejdemyhr D. Athley F.: "DBT, A MATLAB Toolbox
%       for Radar Signal Processing. Reference Guide",
%       FOA-D--9x-00xxx-408--SE, To be published.
%
%  [2]: Kingsley S., Quegan S.: "Understanding Radar Systems",
%       McGraw-Hill 1992.
%
%  [3]: Horner R.A., Johnson, C.R.: "Topics in matrix Analysis",
%       Cambridge University Press 1991.
%
%See also:
%  defnoise, simradarsig, simtarget, simclutter, simjammer.

%   *  DBT, A Matlab Toolbox for Radar Signal Processing  *
%  (c) FOA 1994-2000. See the file dbtright.m for copyright notice.
%
%  Initiation    : 980511 David Rejdemyhr (davrej).
%  Latest change : $Date: 2000/10/16 15:21:54 $ $Author: svabj $.
%  $Revision     : 1.0 $
%*************************************************************************

%-------------------------------------------------------------------------
%----                     Initialize variables.                       ----
%-------------------------------------------------------------------------

noise3D = 0;


%-------------------------------------------------------------------------
%----                  Initialize random generator.                   ----
%-------------------------------------------------------------------------

randn('seed',sum(100*clock));
rand('seed',sum(100*clock));


%-------------------------------------------------------------------------
%----                     Simulate noise signals.                     ----
%-------------------------------------------------------------------------

for noiseIdx = 1:length(noiseSources.Types)

  if (noiseSources.Types{noiseIdx} == 'Gaussian')
    if (1)
      noise3Dpre = sqrt(noiseSources.Powers{noiseIdx}/2) * ...
                  (randn(noPulses, noRangeBins, noChannels) + ...
                  j*randn(noPulses, noRangeBins, noChannels));
    else
      % This branch is used to test the execution time.
      noise3Dpre = randn(noPulses, noRangeBins, noChannels);
      noise3Dpre = noise3Dpre + j*randn(noPulses, noRangeBins, noChannels);
      noise3Dpre = noise3Dpre * sqrt(noiseSources.Powers{noiseIdx}/2);
    end%if

%  elseif
  else
    dbtwarning('Desired noise type was unknown to simulator, proceeding with no noise.');
    noise3D = 0;
  end %if

  if ~isempty(noiseSources.CorrMxs{noiseIdx})
    % Compute the square root of the source covariance matrix with SVD
    % and color the random variables with the square root of the
    % noise covariance matrix.
    [U,SIG,V] = svd(noiseSources.CorrMxs{noiseIdx});
    usqrtsig = U*sqrt(SIG);
    for rangeIdx = 1:noRangeBins
      noise3Dpre(:,rangeIdx,:) = (usqrtsig* ...
        squeeze(noise3Dpre(:,rangeIdx,:)).').';
    end %for
  end %if

  noise3D = noise3D + noise3Dpre;

end %for


%End Of File -------------------------------------------------------------